JERUSALEM — The recently retired chief of Israel’s internal security agency said on Friday night that he had “no faith” in the ability of the current leadership to handle the Iranian nuclear threat, ratcheting up the criticism of Prime Minister Benjamin Netanyahu and Defense Minister Ehud Barak from the defense and intelligence communities.


“I don’t believe in a leadership that makes decisions based on messianic feelings,” said Yuval Diskin, who stepped down last May after six years running the Shin Bet, Israel’s version of the F.B.I. “I have observed them from up close,” Mr. Diskin said. “I fear very much that these are not the people I’d want at the wheel.”


Echoing Meir Dagan, the former head of the Mossad, Israel’s spy agency, Mr. Diskin also said that the government was “misleading the public” about the likely effectiveness of an aerial strike on Iran’s nuclear facilities.


“A lot of experts have long been saying that one of the results of an Israeli attack on Iran could be a dramatic acceleration of the Iranian nuclear program,” Mr. Diskin said at a community forum in Kfar Saba, a central Israeli city. “What the Iranians prefer to do today slowly and quietly, they would have the legitimacy to do quickly and in a much shorter time.”


The comments followed interviews published last week in which the current chief of the Israeli Defense Force, Lt. Gen. Benny Gantz, appeared to be taking a more moderate approach on Iran than Mr. Netanyahu and Mr. Barak, although aides to all three men later insisted that they were on the same page.


Mr. Diskin has been widely thought to share the views of Mr. Dagan — who has been harshly attacking the government’s approach in speeches and interviews for nearly a year — but this is the first time he has spoken about it publicly. Shin Bet does not deal with foreign affairs, and Mr. Diskin was careful to say that he was not saying that attacking Iran “is not a legitimate decision,” but was instead questioning the leaders’ abilities and their motives for their hawkish policies. Still, his biting statements, coming so soon after Mr. Gantz’s remarks, suggest that Mr. Netanyahu might be facing more of a challenge of his policy on Iran than before.


Mr. Netanyahu and Mr. Barak have made clear for months that they believe urgent action is needed to stop Iran from building a bomb, and that they consider themselves the main decision makers on whether to stage a pre-emptive strike on Iran.


Ronen Bergman, an Israeli analyst and author of the 2008 book “The Secret War With Iran,” said in an interview that Mr. Diskin’s comments were significant because he left the government in good standing with Mr. Netanyahu — unlike Mr. Dagan, who was forced out — and because he was widely respected “for being professional and honest and completely disconnected from politics.”


Still, Mr. Bergman noted the growing chorus of criticisms: “They have an impact, but I wouldn’t say that this is a crucial factor in the decision-making process. The opinion of the current chief of Shin Bet and the chief of Mossad and the current chief of the military are much more critical when it comes to whether to strike Iran or not.”


Meir Javedanfar, an Iranian-Israeli who runs the blog Middle East Analyst, said Mr. Diskin, in his comments, offered an insider’s view of the motivations and decision-making processes of the nation’s leadership. “Israel’s citizens would be forgiven for thinking that when it comes to addressing the Iranian nuclear threat, Netanyahu and Barak rely more on their own self-created image as the messiahs,” Mr. Javedanfar wrote in an e-mail, “than mounting evidence and warnings that such an attack could be counterproductive.”


“The public nature of such warnings by former intelligence officials puts pressure on Netanyahu and Barak,” he added, “because if they attack Iran and it backfires, such warnings could be used against both of them in postwar commissions.”


The prime minister’s office was expected to respond to the comments on Saturday night. A vice prime minister, Silvan Shalom, hinted in an interview with Israel Radio that Mr. Diskin might have political motives, and promised that any decision on attacking Iran would not be made by Mr. Netanyahu and Mr. Barak alone, but in a wider forum.


Indeed, Mr. Diskin did not limit his critique to the policy on Iran. He said Israel had in recent years become “more and more racist,” and, invoking the 1995 assassination of Yitzhak Rabin, said there were many extremist Jews today who “would be willing to take up arms against their Jewish brothers.”